High Resolution Infrared Studies of Molecular Dynamics

Abstract

Reaction dynamics is one of the principal subjects of chemistry. The traditional way of studying this problem relies on inspection of changes in concentration of reactants and products as the reaction proceeds; the result of chemical analysis is employed to infer the details of intermediate processes. Chemical reactions are obviously not as simple as explained merely by means of classical methods of chemical analysis. Many workers have closely examined the individual steps of gas phase reaction processes, i.e. elementary reactions. Such efforts have resulted in the detection of quite a large number of short-lived molecules as reaction intermediates. Identification of these species is a sort of prerequisite for understanding the reaction mechanism. Because most reaction intermediates involve un­ paired electrons, they have attracted a lot of attention in many fields of molecular science. Increasing development of spectroscopic tools has enabled workers to characterize many of them. The high-resolution spectra of reaction intermediates are extremely valuable in examining, in real time, distributions over quantum states of molecules taking part in reac­ tions, which can deviate considerably from the Boltzmann distribution. High resolution molecular spectroscopy and kinetic studies have thus collaborated closely to bring about recent remarkable progress in the study of reaction dynamics. Electronic spectroscopy in the visible and ultraviolet regions, combined with flash photolysis, has been most widely employed in the study of transient molecules as reaction intermediates (1). The development of the dye laser has accelerated this trend, because this light source has made laser-induced fluorescence (UF) easy to apply. This method provides us